1. Field of the Invention
The present invention relates to a silicon-containing surface modifier, a resist lower layer film-forming composition containing the same, and a patterning process.
2. Description of the Related Art
Widely adopted as exposure light to be used upon resist pattern formation in 1980's, were a g-line (436 nanometers) or an i-line (365 nanometers) of a mercury lamp. As means for further scaling-down, shifting to a shorter wavelength of exposure, light was assumed to be effective, so that in a mass-production process after a DRAM (Dynamic Random Access Memory) of a 64M bit (processing dimension of less than 0.25 μm) in 1990's, a KrF excimer laser (248 nm) at a shorter wavelength was used as an exposure light source instead of the i-line. However, in production of DRAMs at integration degrees of 256M, 1G, and higher which require a finer processing technique (processing dimension of 0.2 μm or less), light sources at shorter wavelength were required, thereby resulting in earnest investigations of photolithography adopting an ArF excimer laser (193 nm) in the past ten years. Although the ArF lithography was initially intended to be firstly applied to a device fabrication of a 180 nm node device, the KrF excimer lithography was prolonged in life to a mass-production of a 130 nm node device, such that the ArF lithography was firstly and fully applied to a 90 nm node. Further, such a technique was combined with a lens having an NA increased to as great as 0.9, thereby conducting mass-production of a 65 nm node device. Further shortening of wavelength of the exposure light is progressing in the next 45-nm node device; and for that, the F2 lithography with 157 nm wavelength became a candidate. Unfortunately, the development of F2 lithography was abandoned, due to various burdens such as: an increased cost of a scanner because of usage of a large amount of expensive CaF2 single crystal for a projection lens; a modification of an optical system accompanying to introduction of a hard pellicle instead of a soft pellicle exhibiting an extremely low durability; a deteriorated resistance of a resist film, against etching; and the like; resulting in alternative introduction of ArF liquid immersion lithography.
In the ArF immersion lithography, such a water having a refractive index of 1.44 was introduced between a projection lens and a wafer by a partial filling manner, thereby enabling a high-speed scanning to conduct mass-production of a 45 nm node device by means of a lens having an NA of about 1.3.
Meanwhile, as a candidate of lithography technique for a 32 nm node, vacuum ultraviolet light (EUV) at a wavelength of 13.5 nm has been mentioned. However, the EUV lithography is accompanied by a pile of problems to be overcome, such as a laser to be increased in output, a resist film to be increased in sensitivity, a resolution to be enhanced, a line edge roughness (LER) to be lowered, an MoSi lamination mask to be free of defects, reflective mirror aberrations to be lowered, and the like.
In turn, the high refractive index immersion lithography as another candidate as a technique for a 32 nm node has been abandoned in development, because the LUAG as a candidate of a high refractive index lens exhibits a lower transmittance, and it has been impossible to obtain a liquid having a refractive index increased to a targeted value of 1.8.
As described above, the light exposure having been used as a general-purpose technique is now approaching a limit of an essential resolution inherent to the wavelength of a light source. As such, attention has been again directed to an organic solvent development configured to form such an extremely fine hole pattern by virtue of a negative tone obtained by an organic solvent development, which hole pattern has not been attained insofar as based on a conventional patterning process by a positive tone to be obtained by alkaline development. The organic solvent development is a process configured to adopt a positive resist composition having a higher resolution, and to conduct the organic solvent development, thereby obtaining a negative pattern. Further, even such an investigation is being progressed, to combine two times of developments, i.e., the alkaline development and the organic solvent development, so as to obtain a twice higher resolving power.
Usable as such an ArF resist composition for developing a negative tone by an organic solvent, is a conventional positive ArF resist composition, patterning processes for which are described in Patent Documents 1 to 3, for example.
One of techniques for transferring the thus formed negative tone pattern onto a substrate, is a multi-layer resist method. This technique is configured to: provide, an intermediate film such as a silicon-containing resist lower layer film, which is different in etching selectivity from a photoresist film, i.e., from a resist upper layer film, between the resist upper layer film and a substrate to be processed; obtain a pattern in the resist upper layer film; subsequently transfer the thus obtained pattern onto the resist lower layer film by dry etching, by using the upper layer resist pattern as a dry etching mask; and transfer the thus obtained pattern onto the substrate to be processed, by dry etching, by using the lower layer resist pattern as a dry etching mask.
Examples of the silicon-containing resist lower layer film to be used in such a multi-layer resist method include: a silicon-containing inorganic film based on CVD, such as a SiO2 film (Patent Document 4, for example), and a SiON film (Patent Document 5, for example); a film to be obtained by spin coating, such as an SOG (spin-on-glass) film (Patent Document 6, for example), and a crosslinkable silsesquioxane film (Patent Document 7, for example); and the like.    Patent Document 1: JP2008-281974A    Patent Document 2: JP2008-281980A    Patent Document 3: JP2009-53657A    Patent Document 4: JP7-183194A    Patent Document 5: JP7-181688A    Patent Document 6: JP2007-302873A    Patent Document 7: JP2005-520354A